public class code {
    public static int ZhaoDanShenGou(int[] arr){
        int sz = 0;
        for(int i = 0;i < arr.length;i++){
           sz ^= arr[i];
        }
        return sz;
    }
    public static void main(String[] args) {
        int[] arr = {6,5,4,3,4,5,6};
       int num = ZhaoDanShenGou(arr);
        System.out.println(num);
    }
}
